Siemens 7SC80 Manual page 251

[richtungskennlinien-260602-kn, 1, en_US]
Figure 2-83
The calculation algorithm used filters the measured values so that it is highly accurate and insensitive to
higher harmonics (particularly the 3rd and 5th harmonics – which are often present in zero sequence
currents). Direction determination relies on the sign of active and reactive power.
Since active and reactive components of the current - not the power - are relevant for pickup, current compo-
nents are calculated from the power components. When determining the ground fault direction the active or
reactive components of the ground current in reference to the displacement voltage as well as the direction of
the active and reactive power are evaluated.
For measurements of sin φ (for ungrounded systems) the following applies
•
Ground fault (forward direction), if Q
•
Ground fault (reverse direction), if Q
For measurements cos ϕ (for resonant grounded systems) the following applies
•
Ground fault (forward direction), if P
•
Ground fault (reverse direction), if P
If PHI CORRECTION is unequal 0°, the angle of the directional limit lines is calculated by adding up active and
reactive power components.
Logic
The following figure illustrates the activation criteria of the sensitive ground fault protection. The operational
mode of the ground fault detection can be set under address 3101.
If set to ON, tripping is possible and a fault log is generated.
If set to Alarm Only, tripping is not possible and only a ground fault log is generated.
The pickup of the displacement voltage element V
element drops out, fault recording is terminated (see logic diagrams
The entire function can be blocked under the following conditions:
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Directional characteristic for cos–φ–measurement
E
E
E
< 0 and Ι
E
2.13 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
< 0 and Ι > setting value (RELEASE DIRECT.),
reactive
>0 and Ι > setting value (RELEASE DIRECT.).
reactive
> 0 and Ι > setting value (RELEASE DIRECT.),
active
> setting value (RELEASE DIRECT.).
active
starts the ground fault recording. As the pickup of the V
0
Figure 2-85
Functions
0
and Figure 2-86).
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